The rheological properties of liquid fabric softener formulations are critical for consumer acceptance. A common method of enhancing product appeal and conveying a perception of product richness and efficacy is to increase the apparent thickness of the liquid product. The majority of consumers demonstrate a preference for thicker products over thin products.
A number of ways of increasing viscosity of fabric conditioner compositions are known.
One way is to increase the concentration of quaternary softening active. This, however, is expensive and, therefore, often prohibitive for commercial products. Of course, this approach does not provide a solution in the production of dilute fabric conditioners, where the amount of active is typically limited in the region of from about 2 to 9 wt %.
Another method of increasing viscosity is to add a polymer thickener. There are, however, negative attributes associated with many polymeric thickeners in that they are often non-biodegradable, their addition to the rinse product is technically difficult and such polymer thickened products tend to separate with time and cause redeposition problems.
Also known is to blend the active with fatty alcohol, which increases the product viscosity but leads to poor manufacturing robustness and variability problems.
A further problem that must be considered by the manufacturer of dilute fabric conditioners is the phenomenon of flocculation when fabric conditioner compositions are added to water during a rinse step of a laundry process. “Flocs” are white insoluble precipitates which are visually unacceptable and which reduce the performance of the product. There are several approaches to reducing or eliminating this problem.
It is known, for example, to increase the processing temperature during manufacture of the fabric conditioner in order to reduce the occurrence of flocculation upon use. However, this also reduces the viscosity of the formulation.
Decreasing the amount of fatty alcohol in the fabric conditioner composition can also reduce the level of flocculation but again only at the expense of product viscosity.
The use of milling, during manufacture, is also known to reduce flocculation and viscosity.
The addition of non-ionic materials such as non-ionic surfactants is known to break up flocs but is also well known to reduce viscosity.
US2003/0220217 (Unilever) discloses fabric conditioner compositions comprising a cationic softening agent and a defined silicone material to reduce the drying time of laundered fabrics and/or to increase the rate of water removed from the fabrics during the spin cycle of an automatic washing machine. Nonionic surfactants are preferred adjuncts for the purpose of stabilising the compositions. Fully hardened softening agents are preferred and exemplified.
WO99/50378 (Unilever) discloses fabric softening compositions comprising from 1 to 8 wt % of one or more quaternary ammonium fabric conditioning compounds, a stabilising agent selected from a non-ionic surfactant or a single long chain alkyl cationic surfactant or mixtures thereof and a fatty alcohol. The fatty alcohol increases the stability of the compositions.
US2008/0176784 (Unilever) discloses fabric conditioner compositions in the form of an aqueous dispersion comprising an ester linked quaternary ammonium fabric softening material and an alkoxylated non-ionic material to improve high temperature storage stability.
We have now surprisingly found that the combination of a specific quaternary active with a flocculation prevention agent, which is a non-ionic surfactant, enables the formation of a thick “dilute” fabric conditioner composition, which does not flocculate upon use. The quaternary softening active has a specific distribution of fatty acids having chains of a defined carbon chain length. The flocculation prevention agent is essential to prevent the formation of flocs when the composition is added to water. Surprisingly, the viscosity of the composition is not compromised. This combination of exceptional viscosity and visual attributes in a dilute fabric conditioner has not been achieved before.